Effects of reforestation on near‐surface saturated hydraulic conductivity in a managed forest landscape, southern Ontario, Canada

Reforestation of previously deforested landscapes often increases soil organic matter content and porosity as the plantation forest ages, leading to increased soil saturated hydraulic conductivity ( K H ). However, the time required for a reforested soil's K H to recover to that of the original forest differs considerably between locations because of variations in forest, climatic and soil properties. We examined a chronosequence of sites on similar soils in a managed forest landscape in southern Ontario, Canada, ranging from open fields deforested in the late 19th century, through red pine ( Pinus resinosa ) stands of varying age, to 100+ year‐old mixed conifer–hardwoods. Soil texture, organic matter content, bulk density, K H , and overstory and understory forest characteristics were measured. For sites with similar soil textures, there was a general increase in K H in the following sequence: open fields → red pine plantations → mixed conifer–hardwood stands. There were no significant changes in near‐surface organic matter contents or soil bulk densities with forest age, and neither factor was related to temporal changes in K H . Temporal trends in K H were associated with increased understory density with forest age, suggesting that increases in K H were driven by understory root development and greater macroporosity. It may take ~25 years before reforestation begins to affect soil infiltration characteristics at the stand scale and at least 40 years following planting before the K H of soils under red pine plantations begins to equal that for undisturbed mixed conifer–hardwood stands. This recovery may be assisted by management activities such as thinning of red pine stands, which promotes understory development.